Under a White Sky: The Nature of the Future

by Elizabeth Kolbert

The Volcanic Explosivity Index was developed in the 1980s as sort of a cousin to the Richter scale. The index runs from zero, for a gentle burp of an eruption, to eight, for a “mega-colossal,” epoch-making catastrophe. Like its better-known relative, the VEI is logarithmic, so, for example, an eruption has a magnitude of four if it produces more than a hundred million cubic meters of ejecta and a magnitude of five if it produces more than a billion. In recorded history, there have been only a handful of magnitude sevens (a hundred billion cubic meters) and no eruptions of magnitude eight. Among the sevens, the most recent—and, hence, the best chronicled—is the eruption of Mount Tambora, on the Indonesian island of Sumbawa. Tambora fired its first warning shots on the evening of April 5, 1815. People across the region reported hearing loud booms, which they attributed to cannon fire. Five days later, the mountain issued a column of smoke and lava that reached a height of twenty-five miles. Ten thousand people were killed more or less immediately—burned to cinders by the clouds of molten rock and searing vapor that raced down the slopes.

Never heard of this volcano!